1. Field of the Invention
The present invention relates to wet motor fuel pumps and, more particularly, to a wet motor fuel pump of the type wherein the fuel flows in a channel past the armature and, while not operating, produces vapor pressures that must be relieved, and/or is for any other reason filled with matter in a vapor state.
2. Description of the Prior Art
In wet motor fuel pumps where fuel flows past a rotating armature in channels, such as between the juxtaposed axial sides of the motor magnets, the armature windage induces radially-oriented hydraulic curls in the radially disposed channels, such curls creating a turbulence. Moreover, the comparatively narrow circumferential width of the channel when compared to its length induces circumferentially oriented curls, introducing more turbulence. Added to these two sources of turbulence is that introduced by the hydraulic equivalent of a multi-blade turbine siren. The extreme turbulence produced by these three phenomena reduces the effective intermagnet channel area to a small portion of the available cross-sectional area, with the result that neither the maximum available increase in flow rate past the armature nor the maxiumum available reduction in required armature current is obtained. A further problem exists in properly positioning the axial flow channel axially and circumferentially with respect to the outlet port of the pump outlet plate and the outlet passage of the outlet housing of the pump.
A further problem with any fuel pump of the gerotor type is that such pump when rotating at its normal rates is not sufficiently efficient to pump gases, such as fuel vapors, as compared to liquids, such as fuel gas. The generation of fuel vapors in any fuel pump is a common occurrence. Gerotors meeting less than the tightest tolerances on the tip clearances and also flatness and parallelism are unable to self prime themselves. But in a gerotor pump of the type having a check valve in the pump outlet to prevent backflow from the engine, such vapor pressures continue to build as the motor continues to spin and generate heat. The little fluid that may be introduced through the pump inlet is vaporized to a level where the vapor pressure forces the fuel back out of the inlet.